Changes

===Geometry and Site Layout===

===Geometry and Site Layout===

Permeable paving can be used for entire parking lot areas or driveways and can be designed to receive runoff from adjacent impervious surfaces. For example, the parking spaces in a parking lot may be permeable pavers while the drive lanes themsevles are impervious asphalt.  

Permeable paving can be used for entire parking lot areas or driveways and can be designed to receive runoff from adjacent impervious surfaces. For example, the parking spaces in a parking lot may be permeable pavers while the drive lanes themselves are impervious asphalt. In general, the impervious area should not exceed 1.2 times the area of the permeable paving which receives the runoff. A hybrid permeable paving/[[infiltration chamber]] design can feature connection of a roof downspout directly to the stone reservoir of the permeable paving system, which is sized to store runoff from both the pavement surface and the roof drainage area.  

 

In general, the impervious area should not exceed 1.2 times the area of the permeable pavement which receives the runoff.  

A hybrid permeable pavement/soakaway design can feature connection of a roof downspout directly to the stone reservoir of the permeable pavement system, which is sized to store runoff from both the pavement surface and the roof drainage area.  

===Pretreatment===

===Pretreatment===

In most designs, the surface acts as pretreatment to the stone reservoir below. Periodic vacuum sweeping and preventative measures like not storing snow or other materials on the pavement are critical to prevent clogging. Another pretreatment element is a pea gravel choking layer above the coarse gravel storage reservoir.

In most designs, the surface acts as pretreatment to the stone reservoir below. Periodic vacuum sweeping and preventative measures like not storing snow or other materials on the pavement are critical to prevent clogging. Another pretreatment element is to have a [[choking layer]] above the coarse gravel storage reservoir.

===Landscaping===

===Landscaping===

Landscaped areas must drain away from permeable pavement to prevent sediments from running onto the surface. Urban [[trees]] will benefit from being surrounded by permeable pavement rather than impervious cover, because their roots receive more air and water. Interlocking pavers used around the base of a tree may be removed as the tree grows.

Landscaped areas must drain away from permeable paving to prevent sediments from running onto the surface. Urban [[trees]] will benefit from being surrounded by permeable paving rather than impervious cover, because their roots receive more air and water. Interlocking pavers used around the base of a tree may be removed as the tree grows.

===Risk of Groundwater Contamination===

===Risk of Groundwater Contamination===

===Heavy Vehicle Traffic===

===Heavy Vehicle Traffic===

Permeable pavement is not typically used in locations subject to heavy loads. However, some permeable pavers are designed for heavy loads and have been used in commercial port loading and storage areas.

Permeable paving is not typically used in locations subject to heavy loads. However, some permeable pavers are designed for heavy loads and have been used in commercial port loading and storage areas.

===Setbacks from Buildings===

===Setbacks from Buildings===

Permeable pavement should be located downslope from building foundations. If the pavement does not receive runoff from other surfaces, no setback is required from building foundations. Otherwise, a minimum setback of 4 m down-gradient from building foundations is recommended.

Permeable paving should be located downslope from building foundations. If the paving does not receive runoff from other surfaces, no setback is required from building foundations. Otherwise, a minimum setback of 4 m down-gradient from building foundations is recommended.

===On Private Property===

===On Private Property===

If permeable pavement systems are installed on private lots, property owners  or managers will need education on their routine maintenance needs, understanding the long-term maintenance plan. They may also be subject to a legally binding maintenance agreement. An incentive program, such as a storm sewer user fee based on the area of impervious cover on a property that is directly connected to a storm sewer, could be used to encourage property owners or managers to maintain existing practices.

If permeable paving systems are installed on private lots, property owners  or managers will need education on their routine maintenance needs, understanding the long-term maintenance plan. They may also be subject to a legally binding maintenance agreement. An incentive program, such as a storm sewer user fee based on the area of impervious cover on a property that is directly connected to a storm sewer, could be used to encourage property owners or managers to maintain existing practices.

==Design==

==Design==